Illumination device

ABSTRACT

An organic EL device as an illumination device includes a device substrate as a first substrate having a first surface and a second surface, and a conductor portion provided on the first surface of the device substrate and overlapping the periphery of a luminescent section or at least a part of a region where the luminescent section is provided, when seen in a plan view. The conductor portion includes a conductive material and detects the temperature of the luminescent section.

BACKGROUND

1. Technical Field

The present invention relates to an illumination device.

2. Related Art

It is known that an organic EL (Electro-Luminescence) material used forlight emitting elements of an organic EL panel which is an example of anillumination device has a problem that the luminance of emitted lightvaries, depending on the ambient temperature, due to temperaturecharacteristics unique to the material. Because of the uniquetemperature characteristics of the material, particularly, anillumination device suffers a considerable reduction in display qualityor “uneven luminance”. The “uneven luminance” mentioned herein isoriginated from a change (deviation) in the I-L characteristics(current-optical output characteristics) that is caused by a temperaturedifference which may occur in the surface of the substrate(particularly, near the center of the substrate and near the peripherythereof).

JP-A-2007-234447, for example, discloses the technique of detecting thetemperatures of a plurality of portions by means of a temperaturedetector to thereby detect the temperature of the luminescent section sothat high-quality image display without uneven luminance is achieved.Further, JP-A-2008-181008, for example, discloses the technique of usinga plurality of portions in the luminescent section as light emittingportions and also using the portions as portions whose temperatures areto be detected to thereby accurately detect the drive temperature of theluminance element.

JP-A-2007-234447 discloses the temperature detector provided on anopposing substrate, however, a method of detecting the temperature isnot specifically described therein. JP-A-2008-181008 discloses thetechnique using wires and switches for detecting the temperature,resulting in a higher cost.

SUMMARY

An advantage of some aspects of the invention is to provide a low-costillumination device which detects the temperature of a light emittingelement.

Some aspects of the invention may be achieved as the followingembodiments or application examples.

APPLICATION EXAMPLE 1

An illumination device according to the application example 1 of theinvention includes a first substrate having a first surface and a secondsurface, a luminescent section provided on the first surface of thefirst substrate and having a light emitting element, and a conductorportion overlapping a periphery of the luminescent section or at least apart of a region where the luminescent section is provided, when seen ina plan view. The conductor portion includes a conductive material anddetects a temperature of the luminescent section.

When the illumination device according to the application example 1 isin operation, applying a current to the light emitting element causes aluminance layer to emit light. In this case, the luminance of theluminescent section is controlled by the applied current. At the time ofsuch an operation, heat generated when the light emitting element emitslight and heat generated by the wiring resistance or the like may varythe temperature of the luminescent section. The light emitting elementoften has the temperature characteristics such that when the temperaturein use varies, the luminance of emitted light in relation to the appliedcurrent varies, so that the luminance of the pixel section is likely tovary according to a change in the temperature of the pixel section.

According to the application example 1 of the invention, the conductorportion which detects the temperature of the luminescent section isprovided so as to overlap the periphery of the luminescent section or atleast a part of the region where the luminescent section is provided,when seen in a plan view. This configuration allows the temperature ofthe light emitting element to be detected at a low cost without adding aswitch for temperature detection.

The word “detection” by the conductor portion is equivalent to directdetection or measurement made by the conductor portion in a narrowsense, and may include the cases of indirectly detecting, calculating,assuming, predicting, forecasting and specifying the temperature basedon another parameter or a plurality of other parameters relating to thetemperature of the luminescent section in a broad sense.

As described above, the illumination device according to the applicationexample 1 of the invention can detect the temperature of the luminescentsection using the conductor portion.

APPLICATION EXAMPLE 2

The illumination device according to the application example 1 mayinclude a plurality of terminal portions provided on the first surfaceof the first substrate to connect to an external circuit provided incorrespondence to the conductor portion.

This configuration can easily establish connection to an externalcircuit.

APPLICATION EXAMPLE 3

In the illumination device according to the application example 2, theplurality of terminal portions may be disposed close to one another.

Since the terminal portions are located close to one another, it is easyto design an external FPC so that the FPC can be miniaturized.

APPLICATION EXAMPLE 4

The illumination device according to the application example 1 mayinclude a drive control circuit that controls a drive waveform to beapplied to the light emitting element so that the light emitting elementemits light with a predetermined luminance according to the temperaturedetected by the conductor portion.

According to this configuration, the luminance of the luminescentsection can be controlled to be a desired luminance by applying acurrent according to the temperature detected by the conductor portionto the light emitting element. That is, a change in luminance of emittedlight or a deviation from a desired luminance caused by a change in thetemperature of the light emitting element can be reduced or preventedby, for example, detecting the temperature at every predetermined timeby means of the conductor portion during the operation of theillumination device, and applying the application current which iscorrected to provide the desired luminance based on the detectedtemperature to the light emitting element.

APPLICATION EXAMPLE 5

In the illumination device according to the application example 1, theconductor portion may have a linear shape repeatedly cranked.

This configuration increases the resistance of the conductor portion,thereby improving the detection sensitivity to a change in temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a block diagram showing the general configuration of anorganic EL device according to a first embodiment.

FIG. 2 is a schematic cross-sectional view along line II-II in FIG. 1.

FIG. 3 is a diagram showing the resistivity of Mo in the organic ELdevice according to the first embodiment.

FIG. 4 is a block diagram showing a method of driving the organic ELdevice according to the first embodiment.

FIG. 5 is a block diagram showing the general configuration of anorganic EL device according to a second embodiment.

FIG. 6 is a block diagram showing the general configuration of anorganic EL device according to a third embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the invention will be described below withreference to the accompanying drawings. An organic EL device as anexample of the illumination device will be described in the followingdescription of the embodiments by way of example.

First Embodiment

First, the general configuration of an organic EL device according tothe first embodiment will be described referring to FIG. 1.

FIG. 1 is a block diagram showing the general configuration of theorganic EL device 2 according to the first embodiment.

The organic EL device 2 includes a device substrate 40 as a firstsubstrate, a luminescent section 14 provided on a first surface of thedevice substrate 40, and a conductor portion 45 overlapping theperiphery of the luminescent section 14 or a part thereof when seen in aplan view.

The organic EL device 2 is connected to a drive circuit 24 and a drivecontrol circuit 26. As will be described later, the drive controlcircuit 26 generates correction data to be described later based ontemperature data relating to the resistance of the conductor portion 45provided at the periphery of the luminescent section 14, and outputs thecorrection data to the drive circuit 24.

Next, the specific configuration of the organic EL device 2 according tothe embodiment will be described referring to FIG. 2. FIG. 2 is aschematic cross-sectional view along line II-II in FIG. 1.

As shown in FIG. 2, the organic EL device 2 includes the devicesubstrate 40, an organic EL element 12 formed above the device substrate40, and a sealing substrate (not shown). Although the organic EL element12 is a top-emission type organic EL element which emits light upward inthe diagram, it may be a bottom-emission type organic EL element.

The device substrate 40 is formed by, for example, a glass substrate orthe like.

The organic EL element 12 includes an organic EL layer 42, a cathode 44and an anode 46.

The anode 46 is formed above an insulating interlayer 54 and aplanarized film 50 which are sequentially formed on the device substrate40. The anode 46 is, for example, a transparent electrode formed of atransparent material, such as ITO (Indium Tin Oxide), so that lightemitted downward in the diagram from the organic EL layer 42 istransmitted downward. The anode 46 is an electrode formed of, forexample, ITO as a transparent electrode material to a thickness of 100nm or so. A reflection film 51 of Mo (Molybdenum) is provided under theanode 46 (on the planarized film 50 side) via an insulating layer. Thereflection film 51 reflects light emitted from the organic EL layer 42toward the sealing substrate. The material for the reflection film 51 isnot limited to Mo, and any material may be used as long as thereflection film 51 has a capability (reflection surface) of reflectingemitted light. For example, various approaches are available including ascheme of forming a reflection surface having an uneven surface using aninsulating organic material or inorganic material, and a scheme offorming the anode 46 using a conductive material having a reflectioncapability and forming an ITO film on the surface layer of the anode 46.

The cathode 44 is a common electrode which is shared by organic ELelements 12 formed on the device substrate 40. The cathode 44 is formedon the top surface of the organic EL layer 42.

The sealing substrate in use is made of transparent glass or the like.

The organic EL device 2 has a so-called top-emission type structurewhere a drive current is supplied between the anode 46 and the cathode44 so that light emitted from the organic EL layer 42 is reflected atthe reflection film 51 and led to the sealing substrate side. Thetop-emission type structure allows both a transparent substrate and anopaque substrate to be used for the device substrate 40. Examples ofopaque substrates include substrates of a heat-curing resin, athermoplastic resin, etc. in addition to substrates obtained bysubjecting a ceramic sheet of alumina or the like or a metal sheet ofstainless steel or the like to an insulation process, such as surfaceoxidization.

According to the embodiment, as shown in FIG. 2, the conductor portion45 is provided above the device substrate 40. The conductor portion 45is formed of a conductive material such as Mo so as to detect thetemperature near the organic EL element 12 in the luminescent section14. The conductor portion 45 detects the temperature near the organic ELelement 12 based on the change in the resistivity of the conductorportion 45. Terminal portions 49 (see FIG. 1) are provided for theconductor portion 45 to detect a change in resistivity.

The temperature dependency of the resistivity of the conductive materialof the conductor portion 45 is used in the method of detecting thetemperature. The resistivity of Mo as the conductive material is shownin FIG. 3 as an example of the temperature dependency. The temperatureis calculated from a change in the resistivity of the conductivematerial. The thickness of the conductive material Mo is, for example,about 150 nm.

According to the related art, additional use of metal wires fortemperature detection increases the cost. According to the embodiment,the conductor portion 45 is formed by the same layer as the reflectionfilm 51, so that the temperature of the organic EL element 12 isdetected without adding a new layer. This enables low-cost temperaturedetection to be achieved.

The conductive material is not limited to Mo, and may be an opaqueconductive material such as a metal containing at least one of Au, Ni,Pt, Ag, Al, W, Ta, Ti, Cu, Cr and the like. The conductor portion 45 mayinclude a thin-film thermistor or thermocouple as long as the materialis a conductive material, or may include a luminous material, such as anorganic or inorganic EL material, or a silicon film doped with a p-typeor an n-type impurity. In this case, the temperature can also bedetected by using a change in temperature characteristics, such as theresistance of the luminous material or the silicon film.

The sealing substrate prevents moisture from entering the organic ELlayer 42 from outside the organic EL device 2. More specifically, thesealing substrate is adhered onto the device substrate 40 by an adhesiveto seal the organic EL element 12 so that the air outside the organic ELdevice 2 does not contact the organic EL element 12. The adhesive toadhere the sealing substrate onto the device substrate 40 includes aheat-curing resin or ultraviolet-curing resin. For example, an epoxyresin, which is one example of the heat-curing resin, is applied to theperipheral portion of the sealing substrate using an applicator unit,such as a dispenser.

Next, a method of driving the organic EL device 2 according to the firstembodiment will be described referring to FIG. 4. FIG. 4 is a blockdiagram showing a method of driving the organic EL device 2 according tothe embodiment.

The organic EL device 2 includes the conductor portion 45 and theluminescent section 14, and the drive control circuit 26 includes atemperature detecting circuit 63 and a control circuit 28. The organicEL device 2, the drive control circuit 26 and the drive circuit 24 areconfigured to exchange data with one another.

When the organic EL device 2 is in operation, as shown in FIG. 4, thetemperature detecting circuit 63 of the drive control circuit 26 detectsthe resistance of the conductor portion 45 at, for example, everypredetermined time, and outputs temperature data relating to thedetected resistance to the control circuit 28.

The control circuit 28 generates correction data relating to a drivewaveform to acquire a desired luminance based on the temperature datafrom the temperature detecting circuit 63, and outputs the correctiondata to the drive circuit 24.

The “correction data” herein is data for changing parameters, such asthe width, height and shape of the drive waveform or the shape of inrushcurrent, in such a way that the difference between the drive waveformwhich is determined according to a preset temperature and the drivewaveform which is determined according to the detected temperaturebecomes smaller.

That is, the correction data is data for reducing (i.e., correcting) thedifference between the application current needed to cause the organicEL layer 42 to emit light with a desired luminance at the presettemperature and the application current needed to cause the organic ELlayer 42 to emit light with a desired luminance at the detectedtemperature.

The drive circuit 24 generates the drive waveform for driving theluminescent section 14 from the correction data and display data fromthe control circuit 28, and supplies the generated drive waveform to theluminescent section 14. As a result, the application current with thedrive waveform according to the detected temperature is applied to theorganic EL element 12. In other words, the temperature detected by thetemperature detecting circuit 63 is fed back to the control circuit 28,so that the application current with the drive waveform adjustedaccording to the temperature of the luminescent section 14 (or theorganic EL element 12) is applied to the organic EL element 12.

Accordingly, even when the temperature of the luminescent section 14changes due to the heat generated when the organic EL element 12 emitslight or a change in the ambient temperature, the luminance of theluminescent section 14 can be controlled to be the desired luminance.

According to the embodiment, as described above, the provision of theconductor portion 45 allows the temperature detecting circuit 63 todetect the temperature at every predetermined time while the organic ELdevice 2 is in operation. The application current with the drivewaveform corrected, on the basis of the detected temperature, to providethe desired luminance is applied to the organic EL element 12, therebysuppressing or preferably preventing a change in the luminance ofemitted light or a deviation of the luminance of emitted light from thedesired luminance due to a change in the temperature of the organic ELelement 12.

Further, referring to FIG. 2, according to the embodiment, thereflection film 51 which is the reflection portion provided on thedevice substrate 40 can be shared as the conductor portion 45. That is,the conductor portion 45 can be formed at a low cost.

As described above, the organic EL device 2 according to the embodimentincludes the conductive portion 45 that is used to detect thetemperature of the luminescent section 14 and the drive control circuit26 that corrects the drive waveform on the basis of the detectedtemperature, thereby enabling high-quality light emission to beachieved. Moreover, the reflection film 51 provided above the devicesubstrate 40 is also used as the conductive portion 45, thereby enablingthe conductive portion 45 to be formed at a low cost.

Second Embodiment

Next, an organic EL device according to a second embodiment will bedescribed referring to FIG. 5.

FIG. 5 is a block diagram similar to FIG. 1 for the first embodiment. Toavoid the redundant description, same reference numerals as used for thecomponents of the first embodiment shown in FIG. 1 are given to thosecomponents in FIG. 5 which are similar to the corresponding componentsof the first embodiment.

In an organic EL device 4 according to the second embodiment, theconductor portion 45 includes a conductive film of the same layer as theanode 46. This embodiment also allows the temperature of the luminescentsection 14 to be detected by measuring the resistance of the conductorportion 45 similarly to the first embodiment. Since the conductorportion 45 is the same layer as the anode 46, it is unnecessary to add anew conductive layer, leading to cost reduction.

Third Embodiment

Next, an organic EL device according to a third embodiment will bedescribed referring to FIG. 6.

FIG. 6 is a block diagram similar to FIG. 1 for the first embodiment. Toavoid the redundant description, same reference numerals as used for thecomponents of the first embodiment shown in FIG. 1 are given to thosecomponents in FIG. 6 which are similar to the corresponding componentsof the first embodiment.

In an organic EL device 6 according to the embodiment, the conductorportion 45 is formed into a single linear shape repeatedly cranked todetect the temperature of the luminescent section 14.

For example, as shown in FIG. 6, the conductor portion 45 is formed intoa single linear shape repeatedly cranked, extending in an up-and-downdirection in the diagram of the luminescent section 14. Therefore, theresistance of the conductor portion 45 increases, so that the detectionsensitivity to a change in temperature can be improved.

Accordingly, the drive control circuit 26 corrects the drive waveform tobe applied to the luminescent section 14 according to a change intemperature based on the improved detection sensitivity, and therefore avariation in the luminance of the luminescent section 14 can be reducedor prevented.

Particularly, when the luminescent section 14 is wide (i.e., the devicesubstrate 40 or the illumination device has a large size), thetemperature distribution of the luminescent section 14 is likely tooccur, which causes variations in the luminance of the luminescentsection 14. Therefore, it is effective to correct the drive waveformaccording to the temperatures of a plurality of luminescent sections 14which are detected by increasing the resistance of the conductor portion45.

The organic EL devices 2, 4 and 6 according to the embodiments eachinclude a plurality of terminal portions 49 disposed near one another asshown in FIGS. 1, 5 and 6, respectively. Since the terminal portions 49are located close to one another according to the embodiments, it iseasy to design an external FPC (not shown) so that the FPC isminiaturized.

This application claims priority from Japanese Patent ApplicationNo.2010-229326 filed in the Japanese Patent Office on Oct. 12, 2010, theentire disclosure of which is hereby incorporated by reference in itsentirely.

1. An illumination device comprising: a first substrate having a firstsurface and a second surface; a luminescent section provided on thefirst surface of the first substrate and having a light emittingelement; and a conductor portion overlapping a periphery of theluminescent section or at least a part of a region where the luminescentsection is provided, when seen in a plan view, the conductor portionincluding a conductive material and detecting a temperature of theluminescent section.
 2. The illumination device according to claim 1,further comprising a plurality of terminal portions provided on thefirst surface of the first substrate to connect to an external circuitprovided in correspondence to the conductor portion.
 3. The illuminationdevice according to claim 2, wherein the plurality of terminal portionsare disposed close to one another.
 4. The illumination device accordingto claim 1, further comprising a drive control circuit that controls adrive waveform to be applied to the light emitting element so that thelight emitting element emits light with a predetermined luminanceaccording to the temperature detected by the conductor portion.
 5. Theillumination device according to claim 1, wherein the conductor portionhas a linear shape repeatedly cranked.